This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 4 |
| 6 | 13 |
| 7 | 44 |
| 8 | 149 |
| 9 | 500 |
| 10 | 1660 |
| 11 | 5444 |
| 12 | 17640 |
| 13 | 56524 |
| 14 | 179322 |
| 15 | 563932 |
| 16 | 1759982 |
| 17 | 5456608 |
| 18 | 16821309 |
| 19 | 51600720 |
| 20 | 157615653 |
| 21 | 479664388 |
| 22 | 1455061181 |
| 23 | 4401607356 |
| 24 | 13282579293 |
| 25 | 39997017088 |
| 26 | 120215762283 |
| 27 | 360730451088 |
| 28 | 1080880047091 |